JP7525517B2 - Immediate Attachment Clamps for External Fixation Systems - Google Patents

Description

The present invention relates to a clamp for orthopedic applications, in particular a clamp for connecting elements constituting an external fixation system.

The present invention is therefore useful in orthopedic surgery, particularly in the field of trauma surgery.

In orthopedic surgery, external fixation techniques are commonly used for stabilization, reduction and alignment of bone fragments. These techniques consist of the surgical application of a rigid exoskeleton, which in its simplest form consists of several rod members articulated to each other by suitable clamps and connected to the patient's bone structure by screws. The mechanical system employed is globally referred to as an external fixator.

The diversity of treatment requirements has contributed to the development of various types of fixators, each with technical and morphological characteristics adapted to their application. Thus, for certain applications, most often in critical traumatic injuries, the so-called immediate fixators have been developed, which are characterized precisely by the simplicity and speed of fixation.

Immediate fixators consist of structural rods connected to various clamps that are either intended to connect the rods to each other at a structural joint (rod-rod clamps) or serve to connect the rods to through-screws that are not fixed to the patient's bone (rod-screw clamps). All of these clamps are elements with specific design considerations and must balance the competing requirements of ease of tightening and stability of fixation.

In this context, immediate fixation systems have been proposed on the market that include multiple elements that can be assembled in different ways to meet specific surgical requirements.

In particular, these systems have different types of attachments, for example rod attachments and screw attachments that can be joined together by means of a joint screw. The surgeon must therefore assemble at least two attachments and a joint screw to form a clamp. In these systems, the rod attachments generally have a C-shape. A rod is introduced between the two arms of this C-shaped element and is fixed by tightening the joint screw.

Although systems of the above types perform the functions they perform in a satisfactory manner, they nevertheless have some drawbacks that remain unsolved to date.

The first drawback concerns the insertion of the rod during surgery. The transverse insertion of the rod, i.e. transverse to the direction in which the rod extends, is generally easier than the longitudinal insertion, especially in implants where two bone screws are already fixed in the same base and an intermediate screw is added. Transverse insertion is also preferred when the rod extends axially to a significant extent and when the alignment of the different clamps supporting the rod is checked during surgery. However, in known types of C-shaped systems, transverse insertion requires the withdrawal of the joint screws that hold the clamp attachments, and therefore the clamps must be completely disassembled and the assembly re-tightened after the rod insertion. In some cases, the arms of the rod attachment are kept separated by a spacer, which must be removed and re-inserted to allow the rod to be inserted. Transverse insertion is therefore understood to be a complex operation and requires a considerable amount of time for the surgeon to perform it during surgery.

A second drawback arises from the need to disassemble the device for some applications. This operation in fact carries a significant risk of dropping and/or losing several individual parts, especially if disassembly has to be performed during surgery.

A third drawback is the weight of the fixator, which is usually made up of multiple rods and multiple clamps altogether, due to the type of material used.

A further drawback is that the number of parts that make up the clamp is significant, which makes the assembly expensive to manufacture.

The technical problem underlying the present invention is therefore to overcome at least some of the drawbacks reported in the prior art and in particular to provide a clamp that makes the implantation of an external fixator into a patient easier and less risky.

The solution idea behind the present invention is to provide an auxiliary connection means that keeps the clamp connected in the open configuration to allow lateral insertion of the rod member, allowing the surgeon to manipulate the clamp's components before tightening.

Therefore, the above technical problem is solved by a clamp for an external fixator, in particular a clamp of the immediate attachment type, having the following features: That is, the clamp of the present invention comprises at least one first attachment having at least one rod member receiving seat for a rod member of an external fixator and/or at least one screw receiving seat for a bone screw, at least one second attachment having at least one rod member receiving seat, and a connector that passes through the first attachment and the second attachment in a tightened configuration to integrate the first attachment and the second attachment with each other and secure the rod member and/or the bone screw in the rod member receiving seat and/or the screw receiving seat, and the clamp can be further configured in an open configuration in which the connector is at least partially withdrawn from the second attachment, thereby allowing lateral insertion into the rod member receiving seat, and the clamp comprises an auxiliary connection means that keeps the first attachment and the second attachment connected to each other in the open configuration.

The device thus employed allows the clamp to assume a stably coupled open configuration. In particular, this open configuration allows for lateral insertion into at least one of the rod member receiving seats that are normally closed by the connector.

Lateral insertion is particularly advantageous because it aids the orthopedic surgeon in sequentially aligning the clamps that must hold the rod member, especially when the rod member is held by more than two aligned clamps.

Furthermore, the binding of the clamp in the open configuration prevents the loss or dropping of multiple individual parts, thereby making the clamp easier and safer to operate, primarily during surgery.

Preferably, the connector comprises a head portion accessible to a user at a first end of the clamp and a stem having at least one threaded portion. The clamp comprises a threaded seat located at a second end thereof. In a clamped configuration, the stem is threaded through the first and second attachments and the threaded portion engages within the threaded seat to secure the rod and/or bone screw within the rod receiving seat and/or screw receiving seat. In an open configuration, the threaded portion is completely disengaged from the threaded seat.

More preferably, the first end of the clamp is on the first attachment side and the second end of the clamp is on the second attachment side, the second attachment having two arms connected by a C-shaped flexible bridge that defines the rod member receiving seat. In the clamped configuration, the stem extends between the two arms and interferes with lateral insertion into the rod member receiving seat. In the open configuration, the stem rises towards the first attachment, thereby allowing lateral insertion into the rod member receiving seat.

The connector may include a stop collar along the stem, preferably at the end of the threaded portion, that limits the maximum tightening of the clamp. In this way, excessive deformation of the attachment itself is avoided without having to resort to a separate spacer, which can be potentially easy to lose and complicated to place.

The stop collar preferably has two flat surfaces that are connected by a conical portion and arranged to be introduced into a corresponding conical seat of the second attachment.

Furthermore, in the open configuration, the stop collar can prevent the connector from being completely withdrawn from the rest of the clamp by interfering with a retaining member that is integral with one of the attachments on the clamp itself.

The auxiliary connection means is advantageous because, in the open configuration, it allows relative axial movement of the second attachment with respect to the first attachment between a first position in which the two coupling surfaces on the first and second attachments are in contact and engaged with each other to prevent relative rotation of the first attachment with respect to the second attachment, and a second position in which the coupling surfaces are disengaged to allow relative rotation of the first attachment with respect to the second attachment, thus allowing the orthopaedic surgeon to adjust the relative orientation of the two attachments in the open configuration.

The interlocking surfaces may include radial teeth, sawtooth, or other elements positioned side-by-side and arranged to engage with one another.

The auxiliary connection means comprises at least one tongue integral with one of the first attachment and the second attachment and at least one coupling seat integral with the other of the first attachment and the second attachment, the at least one tongue sliding axially within the coupling seat until a maximum extension lock is reached, and the at least one tongue is further rotatable within the coupling seat relative to the axis of rotation.

Preferably, the connecting seat is provided on the first attachment, while the tongue is integral with the second attachment.

The maximum extension lock is preferably defined by a narrow portion of the coupling seat against which the outwardly projecting teeth of at least one tongue abut.

Preferably, the tongues are arranged circumferentially about the axis of rotation and are deformable inwardly to allow for snap coupling within the coupling seat.

More preferably, the number of tongues is two, and the two tongues face each other.

The axial displacement between the above-mentioned attachments, which is made possible by the auxiliary connecting means, is preferably such that the tongues are accessible by the operator. By pressing the two tongues from opposite sides, the operator can bend the tongues inwards, thereby releasing the auxiliary connecting means.

Preferably, the one or more tongues are integral with the second attachment and define a lock against withdrawal of the connector in the open configuration.

Preferably, the locking action is performed by a limit stop located at the end of the tongue, opposite the teeth of the tongue itself, which holds the stop collar of the connector. If the tongue is flexible, it can be freely bent outwards so that the connector can pass the limit stop. However, when the auxiliary connection means is connected, the tongue cannot be bent outwards. Under this condition, the outer side of the teeth of the tongue abuts against the inner surface of the connection seat.

It will be appreciated that thanks to the above device, the fixator can be withdrawn, but only after separation of the two attachments that make up the clamp.

The limit stops are preferably located at the ends of cylindrical track portions formed on the inner surfaces of one or more of the tongues.

The tongue or tongues may be integrally formed with one of the two attachments of the connector, preferably the second attachment. Alternatively, the tongues may be formed on a separate insert that is introduced into the central hole of the attachment.

Preferably, the first attachment has at least two screw receiving seats configured to accommodate different sizes of bone screws to suit different anatomical locations or different sizes of bone (e.g., 4mm for wrist/foot, 5mm for upper arm/ankle, 6mm for pelvis/femur/tibia).

More preferably, the first seat can be configured to selectively accommodate two different diameters (e.g., 5 mm and 6 mm). The second seat can be configured to accommodate a third diameter (e.g., 4 mm).

Preferably, the first attachment includes both a screw receiving seat and a rod receiving seat. The possible rod/screw attachment combinations allow for greater ease of assembly as well as flexibility in using the clamp, given that a single component can be selected for a variety of applications.

At the end of the stem, the connector has a coupling profile for a tightening tool, preferably a polygonal recess for a wrench head, e.g. a hexagonal recess for a setscrew wrench, and a tightening knob for manually tightening the connector.

The tightening knob can therefore be conveniently used in a preliminary tightening step, allowing for ergonomic assembly of the system.

Different attachment materials, which are not intended to be exclusive, can be, for example, plastic materials (polyetherimide, polysulfone, polyarylamide, etc.) reinforced with glass or carbon fibers, intended to combine low cost, mechanical resistance and sterility.

For connectors, simple AISI Class 300 stainless steel, aluminum alloy, or titanium alloy may be used.

Furthermore, it is noted that the particularity of the design of the above attachments, and the lack of tolerance limitations, suggests that 3D printing technology could be used.

The advantage of the above clamp is due to the considerably reduced number of components, i.e. the connector, the two attachments and the nut, which is preferably integrated with the second attachment. This reduces the assembly complexity during production as well as the manufacturing and storage costs.

Further features and advantages will become more apparent from the following detailed description of a non-exclusive preferred embodiment of the invention, with reference to the accompanying drawings, given as non-limiting examples.

FIG. 1 is a perspective view of a first attachment that is part of a clamp for an orthopedic fixator according to the present invention. FIG. 2 is a perspective view of the attachment of FIG. 1 seen from a different angle. FIG. 3 is a perspective view of the attachment of FIG. 1 cut along its midplane; FIG. 4 is a perspective view of a first form of a second attachment that is part of a clamp for an orthopedic fixator according to the present invention. FIG. 5 is a perspective view of the attachment of FIG. 4 cut along the mid-plane. FIG. 6 is a perspective view of a second form of a second attachment that is part of a clamp for an orthopedic fixator according to the present invention. FIG. 7 is an exploded perspective view showing the attachment of FIG. FIG. 8 is an exploded perspective view of the attachment of FIG. 6 cut along the midplane. FIG. 9 is a perspective view of a second embodiment of a connector that is part of a clamp for an orthopedic fixator according to the present invention. 10 is a side view of the connector of FIG. FIG. 11 is a front view showing the connector cut along the plane AA of FIG. FIG. 12 is a perspective view showing a clamp for an external fixator according to the present invention, comprising the first attachment of FIG. 1, the second attachment according to the first embodiment of FIG. 4, and a fixator according to the first embodiment not shown in FIGS. 1 to 11. FIG. 13 is a perspective view of the clamp of FIG. 12 cut along the midplane in a clamped configuration. 14 is a perspective view of the clamp of FIG. 12 cut along its midplane in an open configuration. FIG. 15 is an exploded perspective view of the clamp of FIG. 16 is an exploded perspective view of the clamp of FIG. 12 cut along the midplane; FIG. Figure 17 is a perspective view of a clamp for an external fixator according to the present invention, comprising the first attachment of Figure 1, the second attachment according to the second embodiment of Figure 6, and the fixator according to the second embodiment of Figure 9, in an intermediate configuration between a tightened configuration and an released configuration. FIG. 18 is a perspective view of the clamp of FIG. 17 in an open configuration. 19 is an exploded perspective view of the clamp of FIG. 17. FIG. FIG. 20 shows an external fixator comprising four clamps of the type shown in FIG. 12, a rod member and four bone screws, connected to a long bone of a patient, with the four clamps in an open configuration. FIG. 21 shows an external fixator with six clamps and three bars of the type shown in FIG.

With reference to the attached figures 12 to 19, two embodiments of clamps adapted to act as connecting elements of an orthopedic external fixator, in particular an immediate fixator of the type shown in figures 20 and 21, are identified with the reference signs 1 and 1'. The clamps 1; 1' are arranged so that a temporary fixed connection is made in a quick and effective manner between two connecting rod members 101 having a diameter of 4 mm, 5 mm or 6 mm, or between a rod member 101 having a diameter of 4 mm, 5 mm or 6 mm and a bone screw 102.

Both embodiments of the clamp 1;1' include a first attachment 2 and a second attachment 3;3' held together by a connector 5;5'. The embodiments differ from each other in that they use either a similar but non-identical second attachment 3;3' and either a non-identical connector 5;5'. Other embodiments of the clamp are obtained by various combinations of the first attachment 2, second attachment 3;3' and connector 5;5'.

The first form of connector 5, which can be seen in all of Figures 12-16, comprises a stem 50 having a threaded portion 58 at its end. The opposite end of the stem 50 is provided with a head portion 51 having a rounded shape that is coupled to the stem by a concave surface 52.

The threaded portion 58 of the stem 50 is separated from the non-threaded continuation by a stop collar 57, i.e. a circular flange with frusto-conical sides, which is inserted into a corresponding seat of the second attachment 3; 3'. The stop collar 57 defines a limit stop which limits the maximum tightening of the connector 5. Moreover, as will become clearer from the following description, the same stop collar 57 also provides a retention of the connector 5 in its sliding seat on the clamp 1; 1'.

The head portion 51 has an externally knurled annular nut that defines a gripping portion 54 for manually pre-tightening the connector 5. The connecting profile portion 53, i.e., a hexagonal recess for a set screw wrench, is located separated from the gripping knob 54 by a cavity 56 that opens away from the stem 50.

The second form of connector 5' shown in Figures 9-11, respectively, and part of the assembly shown in Figures 17-19, is substantially similar to that described above, except for the shape of the head portion 51'.

In this case, the head portion 51' actually has a pair of concave gripping portions 54' projecting onto a disk-shaped portion defining a diametrically extending gripping element. This gripping portion 54' has a central connecting profile 53' with a hexagonal recess for a set screw wrench, which connecting profile 53' is similar to that described above for the first embodiment.

The presence of the separate gripping parts 54; 54' and connecting profile parts 53; 53' in the connectors 5; 5' allows the tightening operation to be performed manually initially and then improved further with a suitable tightening tool.

The connector 5; 5' described above is threaded into a tightening nut 55 which defines a threaded seat 59 therein. The nut 55 is located at the end of the connector 5; 5' opposite the head 51; 51' in the clamp 1; 1'. Once threaded into the nut 55, the connector 5; 5' is tightened by compressing the intervening attachment 2, 3; 3'.

As described below, the nut 55 is preferably formed integrally with the second attachment 3; 3'.

As shown in Figures 1-3 respectively, the first attachment 2 is provided with two arms, which are respectively recognized as an inner arm 20 and an outer arm 21 with respect to the overall structure of the assembled clamp 1. The arms 20, 21 are connected by a C-shaped flexible bridge 22, i.e., by a resilient hinge that allows bending in other than the remaining structure, which are mutually parallel parts.

The flexible bridge 22 has an inner cylindrical surface that extends over an arc of a little more than 180° and connects to the planes of the two arms 20, 21. This surface defines a rod receiving seat 26, inside which the connecting rod 101 of the external fixator 100 can be clamped.

At the end opposite the flexible bridge 22, the arms 20, 21 define jaws 27a, 27b, respectively, which are thickened relative to the remainder of the arms and have opposing surfaces, each of which has two V-shaped grooves extending across the attachment. These grooves face the grooves of the opposing jaw and define two screw-receiving seats 23a, 23b. The first screw-receiving seat 23a is positioned to receive a 5 mm or 6 mm screw in a more outboard position relative to the attachment 2, depending on the bending of the arms due to tightening of the connectors 5; 5'.

The second screw receiving seat 23b is instead positioned more medially to receive a 4 mm screw. Thus, the surgeon selects which receiving seat 23a, 23b to use depending on the screw diameter.

Furthermore, the inner arm 20 and the outer arm 21 each have an inner hole 24 and an outer hole 25 for passing the stem 50 of the connector 5. These holes 24, 25 are large relative to the diameter of the stem 50, ensuring sufficient clearance to allow bending of the attachment 2.

Outside the outer through-hole 25, a spherical flare, i.e. a convex seat 28 for the concave surface 52 of the connector 5; 5', is formed, such that the surface 52 rests on the seat 28 in substantial contact even when the outer arm 21 is not perpendicular to the stem 50.

Finally, it is noted that the inner arm 20 is defined in its middle part by a cylindrical bush 29, which has radial teeth arranged to engage with corresponding teeth of the juxtaposed attachment, thereby ensuring bending stability of the clamp 1. Furthermore, a number of protrusions 29b are provided on the outer surface, spaced at equal angular intervals, i.e. at 90° intervals, and can be used as an angular reference to ensure perpendicularity between the connecting rod member 101 and the bone screw 102.

A cylindrical coupling seat 41 is defined inside the cylindrical bushing and extends below the portion of the arm 20 that intersects with the inner through hole 24. The coupling seat 41 has an opening that opens towards the second attachment 3; 3' and is bordered by a stepped narrow portion 42.

The second attachment 3 in the first form is shown in each of Figures 4 and 5.

The second attachment 3 has a structure similar to that of the first attachment 2, except for the differences described below.

First of all, the second attachment 3 does not have a jaw defining a seat for a bone screw. The second attachment 3 also has two arms, an inner arm 30 and an outer arm 31, connected by a C-shaped flexible bridge 32 to the overall structure of the assembled clamp 1.

The flexible bridge 32 also in this case defines a rod member receiving seat 36, inside which the connecting rod member 101 of the external fixator can be clamped.

The two arms 30, 31 each have a hole 34, 35 for passing the stem 50 of the connector 5. Even in this case, these holes have a diameter larger than that of the stem 50.

On the outside of the through hole 35, a hexagonal recess 38 is formed to accommodate a clamping nut 55, which, as described above, can be embedded in the attachment 3, for example by co-molding or by subsequent coupling.

In this case too, the inner arm 30 is defined at its end, but not at its intermediate portion, by a cylindrical bushing 39. This bushing has radial teeth 39a arranged to engage with the teeth of the juxtaposed attachment, and reference projections 39b spaced 90° from each other.

However, unlike the first attachment, the cylindrical bushing 39 does not define a coupling seat therein.

Instead, two opposing tongues 40 extend obliquely above the cylindrical bushing 39 relative to the inner bore 35. These tongues 40, together with the connecting seat 41, define the auxiliary connection means 4, the function of which will be described below in this specification.

The cross section of each tongue 40 defines a circular section. Thus, the tongue 40 has a generally flat inner surface and an opposing outer cylindrical surface. The ends of the outer surface are overlapped by an outwardly projecting flange that defines the lateral teeth 43 of the tongue.

The tongue 40 and the teeth 43 are dimensioned relative to the respective narrow portion 42 such that the tongue 40 can be snap-inserted into the connecting seat 41. Once inserted, the tongue 40 can slide within the cylindrical volume defined by the connecting seat 41. When the teeth 43 abut against the narrow portion 42, they in this case prevent the tongue 40 from being pulled out, thus binding the attachment 3 to the attachment 2. However, in this binding position, the movement of the teeth 43 in the connecting seat 40 allows a relative axial movement between the two attachments 2, 3; 3'. Due to the cylindrical shape of the tongue 40 and the connecting seat 41, a relative rotational movement between the two attachments 2, 3; 3' about their central axis of rotation X is also possible, where the two attachments 2, 3; 3' are sufficiently spaced from each other to avoid mutual engagement of the radial teeth 39a and 39b.

The tongue 40 is moderately flexible. By shifting the two mutually engaged attachments 2, 3; 3' from each other to the maximum extent, the operator can manipulate the tongue 40, deforming it inwards and separating the teeth 43 from the narrow portion 42. Thus, the two attachments 2, 3; 3' are separated.

The inner surface of the tongue 40 defines a cylindrical track 44 that is open to the inside of the attachment 3. This track runs up to and ends above the limit stop 45. Once the clamp is assembled, the outer periphery of the stop collar 57 can slide in the cylindrical track 44 until it abuts against the limit stop 45, thereby preventing the connector 5; 5' from being fully extracted. To fully disassemble the clamp 1; 1', it is first necessary to separate the tongue 40 from the connecting seat 41. The tongue 40 is then no longer constrained in the connecting seat 41 and can therefore deform outwardly releasing the stop collar 57 of the connector 5; 5'.

The second attachment 3' in the second form, shown in each of Figures 6 to 8, is substantially identical to the first form, except that the tongue 40 is formed on an insert 46. This insert 46 has a common flanged base which is interference-inserted into the inner bore 34 of the cylindrical bush 39. Said flange abuts against the lower face of the inner bore 34, defining the correct fixing position.

Besides the conventional clamped configuration in which the clamped fixator 5;5' fixes the rod 101 and/or bone screw 102 at the desired position, the clamp 1;1' can also be in an open configuration in which the clamp is used to laterally introduce the rod into the receiving seat 36 of the second clamp 3;3' during surgery, e.g. to check whether the clamps are aligned to be connected to the rod 101, as shown in attached FIG. 20.

This open configuration results in the threaded portion 58 of the connector 5; 5' being out of engagement with the nut 55 and being withdrawn until the stop collar 57 reaches the limit stop 55 defined on the inside of the tongue 40. In this configuration, the connector 5; 5' thus allows full freedom of lateral insertion of the second clamp 3; 3' into the receiving seat 36. The first clamp 2 and the second clamp 3; 3' are no longer held by a screw connection, but remain connected by the auxiliary connection means 4 mentioned above, which allows relative rotation about the rotation axis X between the two components of the clamp 1; 1'.

Obviously, in order to meet certain conditional requirements, a person skilled in the art may make some modifications or variations to the above invention, but all these modifications or variations fall within the scope of protection of the invention as defined in the following claims.

Claims (10)

A clamp (1; 1') for an external fixator (100), comprising:
The clamp (1;1')
At least one first attachment (2) having at least one rod receiving seat (26) for a rod member (101) of the external fixator (100) and/or at least one screw receiving seat (23a, 23b) for a bone screw (102);
at least one second attachment (3; 3') having at least one rod receiving seat (36);
a connector (5; 5') which passes through the first attachment (2) and the second attachment (3; 3') in a clamped configuration to unite them with one another and to secure the rod (101) and/or the bone screw (102) in the rod receiving seat (26, 36) and/or the screw receiving seat (23a, 23b);
Equipped with
the clamp (1;1') may further be configured in an open configuration in which the connector (5;5') is at least partially withdrawn from the second attachment (3;3'), thereby allowing lateral insertion into the rod receiving seat (36);
The clamp (1;1') comprises auxiliary connection means (4) which hold the first attachment (2) and the second attachment (3;3') together in the open configuration , preventing complete separation of the first attachment (2) and the second attachment (3;3') when the first attachment (2) and the second attachment (3;3') are pulled away from each other . The connector (5; 5')
a user-accessible head portion (51; 51') at a first end of the clamp (1);
a stem (50) having at least one threaded portion (58);
Equipped with
The clamp (1) is provided with a screw seat (59) at its second end,
In the clamped configuration, a stem (50) is passed through the first attachment (2) and the second attachment (3) and the threaded portion (58) engages with the threaded seat (59) to secure the rod (101) and/or the bone screw (102) within the rod receiving seat (26, 36) and/or the screw receiving seat (23a, 23b);
2. The clamp (1; 1') for an external fixator (100) according to claim 1, wherein in the open configuration, the threaded portion (58) is fully disengaged from the threaded seat (59). the first end of the clamp (1; 1') is located on the side of the first attachment (2) and the second end of the clamp (1; 1') is located on the side of the second attachment (3; 3'),
said second attachment (3; 3') comprises two arms (30; 31) connected by a C-shaped flexible bridge (32) defining a rod receiving seat (36);
In the clamped configuration, the stem (50) extends between the two arms (30; 31) to interfere with lateral insertion into the rod receiving seat (36);
3. The clamp (1; 1') for an external fixator (100) according to claim 2, wherein in the open configuration, the stem (50) rises in the direction of the first attachment (2), thereby allowing lateral insertion into the rod member receiving seat (36). A clamp (1; 1') for an external fixator (100) according to claim 3, wherein the connector (5; 5') is provided with a stop collar portion (57) arranged along the stem (50) to limit the maximum tightening of the clamp (1). A clamp (1; 1') for an external fixator (100) according to claim 4, wherein the stop collar portion (57) prevents the connector (5) from being completely withdrawn from the remainder of the clamp (1) in the open configuration. The auxiliary connection means (4) in the open configuration has the following features:
a first position in which two coupling surfaces (29a, 39a) provided on the first attachment (2) and the second attachment (3; 3'), respectively, come into contact and engage with each other to prevent relative rotation of the first attachment (2) with respect to the second attachment (3; 3');
a second position in which the coupling surfaces (29a, 39a) are separated from each other to allow relative rotation of the first attachment (2) with respect to the second attachment (3; 3');
The clamp (1; 1') for an external fixator (100) according to any one of claims 1 to 5, which allows a relative axial movement of the second attachment (3; 3') with respect to the first attachment (2) between the first attachment (2) and the second attachment (3). The auxiliary connection means (4) is
at least one tongue (40) integral with one of said first attachment (2) and said second attachment (3; 3');
at least one coupling seat (41) integral with the other of said first attachment (2) and said second attachment (3; 3');
Equipped with
7. The clamp (1; 1') for an external fixator (100) according to claim 6, wherein the at least one tongue (40) slides axially in the connecting seat (41) until it reaches a stop defining a maximum extension, and the at least one tongue (40) is further rotatable in the connecting seat (41) relative to an axis of rotation (X). 8. A clamp (1; 1') for an external fixator (100) according to claim 7, wherein the stop portion defining the maximum extension is defined by a narrow portion (42) of the connecting seat (41) against which an outwardly projecting tooth portion (43) of the at least one tongue-shaped portion (40) abuts. said tongues (40) being a number of tongues arranged circumferentially about the axis of rotation (X) and deformable inwards to allow a snap connection in said coupling seat (41);
A clamp (1; 1') for an external fixator (100) according to claim 8. The clamp (1; 1') for an external fixator (100) according to any one of claims 7 to 9, wherein the at least one tongue portion (40) is integrated with the second attachment (3; 3') and defines a locking portion against withdrawal of the connector (5, 5') in the open configuration.

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